Coronary artery stenting is widely accepted as the treatment of choice for most cases of coronary artery disease (CAD). Implantation of the drug-eluting stents (DESs), in comparison with the bare-metal stents (BMS), has conferred better outcomes for coronary artery stenting.^1–4 Although the administration of the first-generation DES showed a higher rate of success than that of the BMS, doubts were raised over its safety because of the reported cases of late stent thrombosis and very late restenosis.⁵ The link between late stent thrombosis and incomplete endothelial coverage of the stent struts caused changes in the design and materials of the platforms and polymers of the stents.⁶ Randomized controlled trials and studies have revealed promising results after the implantation of the zotarolimus- and the everolimus-eluting stents, in comparison with the first-generation DES and the BMS.^7–9 On the other hand, concerns about late stent failure caused by untoward reactions to the stent polymer led to the introduction of a new-generation DES in which polymers degrade after the termination of drug release.¹⁰ In these stents, drug release lasts about 28 days and an abluminal biodegradable polymer is absorbed after 6 to 9 months, thus turning the DES into a BMS and, theoretically, averting late stent failure as a result of reaction to polymers. Trials have shown the noninferiority of the biodegradable-polymer biolimus-eluting stent (BP-BES) to the previous generations of DESs; however, only a few investigators have compared the biodegradable-polymer with the durable-polymer DES in real-world registries.^11,12 Further analysis of large and comprehensive data registries seemed to be necessary to compare the efficacy and safety of those stents.

During a 12-month follow-up period, we compared the incidence of major adverse cardiac events (MACE) in patients who underwent percutaneous coronary intervention (PCI) with the biodegradable-polymer biolimus-eluting stent (BP-BES) versus the incidence of MACE in patients who underwent PCI with the durable-polymer everolimus-eluting stent (DP-EES).

Patients and Methods

We conducted a retrospective registry analysis of all patients presenting with CAD who had undergone PCI with the BP-BES or DP-EES in Tehran Heart Center from January 2007 through December 2011. Biomatrix^® (Biosensors International; Morges, Switzerland) and Nobori^® (Terumo; Tokyo, Japan) stents were used in the BP-BES group, and the Xience® V or Prime® (Abbott Vascular; Santa Clara, Calif) and Promus® (Boston Scientific Corporation; Natick, Mass) stents were used in the DP-EES group. Stent selection in the individual case depended solely on each operator's routine judgments, but mainly on the proper size for each patient. All the demographic, laboratory, angiographic, procedural, and follow-up data were recorded in the Tehran Heart Center PCI Registry. The exclusion criteria were primary PCI in the presence of acute ST-segment-elevation myocardial infarction (MI) or the presence of cardiogenic shock; a history of coronary artery bypass grafting (CABG) or PCI; and implantation of the 2 different stent types in single or separate sessions of the index procedure. The study complied with the Declaration of Helsinki, and the Medical Ethics Committee of Tehran University of Medical Sciences approved the study protocol.

Before the procedure, all patients were given 70 to 100 U/kg of unfractionated heparin intravenously, 300 to 600 mg of clopidogrel, and 325 mg of aspirin orally; and they were advised to take 80 mg of aspirin and 75 mg of clopidogrel daily for 12 months after discharge from the hospital. Follow-up was performed during the 12th month after the procedure. The primary endpoint was MACE, defined as a composite of death, nonfatal MI, target-vessel revascularization (either via PCI or CABG), and target-lesion revascularization.

Results

The study population comprised 3,270 patients (mean age, 58.53 ± 10.52 yr), of whom 2,648 (81%) received the DP-EES and 622 (19%) the BP-BES. The baseline characteristics of both groups are summarized in Table I. Hypertension (60.3% vs 54.3%; P=0.006) and chronic lung disease (5.9% vs 3.4%; P=0.004) occurred more often among the BP-BES group. There was no significant difference in the prevalence of diabetes mellitus, dyslipidemia, renal failure, and congestive heart failure between the 2 groups of patients.

TABLE I. Baseline Characteristics of the Study Groups

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The baseline and procedural characteristics of the study patients are presented in Table II. In total, 163 Nobori, 551 Biomatrix, 1,160 Promus, and 2,007 Xience stents were implanted in the 3,270 patients. Coronary angiography revealed that triple-vessel disease was more prevalent in the BP-BES group and that the DP-EES group had more single-vessel disease (P=0.025).

TABLE II. Baseline Lesions and Procedural Characteristics of the Study Groups

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After PCI, 98% of the patients (97.6% of the DP-EES and 99.7% of the BP-BES group) completed their 12 months of follow-up. Sixty-three (1.9%) patients did not complete 12 months of follow-up. There was no significant difference between the follow-up subgroups. Table III shows the incidence rate of MACE in the DP-EES versus the rate in the BP-BES group. There was no significant difference in MACE between the 2 groups at 12 months of follow-up (2.7% vs 2.7%; P=0.984). The potential confounding factors were age, positive family history, renal failure, dyspnea upon exertion (New York Heart Association functional class III/IV), left ventricular ejection fraction, lesions at bifurcation site, and stent length. After adjustment, the cumulative probability of MACE in the BP-BES group did not differ from that of the DP-EES group (HR=0.768; 95% CI, 0.421–1.44; P=0.388) (Fig. 1).

TABLE III. Incidence Rate of MACE in the DP-EES Group versus the BP-BES Group

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Discussion

Results of the present study revealed that, in CAD patients during a 12-month follow-up period, implantation of the biodegradable-polymer DES was similar in efficacy and safety to those characteristics of the durable-polymer DES.

Use of biodegradable polymers in the latest generations of DES is assumed to attenuate the concerns over late stent failure occurring with permanent polymers used in the first-generation DES, because the polymer is completely absorbed after the termination of drug release.^13–17 Trials have revealed the lower rates of MACE in short- and long-term follow-up after the DP-EES implantation in comparison to the earlier generation and have introduced the DP-EES as the standard of DES, versus other design improvements.¹⁸ Investigators have also confirmed the superiority of the BP-BES over the first-generation DES.^19,20 In the Limus Eluted from A Durable vs ERodable Stent Coating (LEADERS) trial,¹⁹ the incidence of MACE was not higher in the BP-BES group than that in the sirolimus-eluting stent group. In that trial, survival curves showed increasing divergence at 1, 2, and 3 years, in favor of the BP-BES. After the establishment of BP-BES's noninferiority to DP-EES in randomized trials,^16,21,22 some recent studies have focused on evaluating the advantages of BP-BES over DP-EES.^11,12 Puricel and colleagues¹² compared clinical outcomes in 200 propensity-score-matched pairs of patients (one treated by EES and the other treated by BES) and reported that, at 24 months after PCI, MACE had occurred in 10.5% of the BP-BES group and in 11.5% of the DP-EES group, with no significant difference. At the one-year follow-up, an analysis of a single-center registry of unrestricted use of EES and Biomatrix BES in 406 propensity-score-matched pairs showed a similar rate of target-lesion failure, stent thrombosis, and patient-oriented composite outcome.¹¹ In accordance with these findings, our present study (with a larger sample size) showed no significant differences in MACE during the first year after BP-BES implantation, a year in which 98% of the patients were successfully monitored.

The incidence of MACE in our study population was 2.7% in both groups, which is relatively lower than incidences in earlier studies. This is almost certainly explained by two factors. First, we excluded patients with acute MI, cardiogenic shock, and histories of CABG and PCI, which probably reduces the incidence of MACE. Second, the mean age of our patients was lower than the mean ages of patients in the other studies. The mean age was 58 years in our study, as opposed to 65 years in the studies by Lee and co-authors¹¹ and Tada and associates,²² and 62 and 63 years in the studies by Smits and colleagues²¹ and Kaiser and associates,¹⁶ respectively.